Development of Variable Structure Fuzzy Logic Controller for Enhanced Load Frequency Control

This paper presents a new method of Variable Structure Fuzzy Logic Controller applied to Load Frequency Control (LFC) problem. For analysis, thermal, hydro and gas turbine power plants have been considered. To control these plants, the conventional Proportional - Integral (PI) controller is used for load tracking and frequency regulation. To dominate the proportional controller action during transient period, the PI controller is replaced by Variable Structure System (VSS) controller. Later, the VSS controller is replaced by means of Fuzzy Logic Controller (FLC). Finally, the Variable Structure Fuzzy Logic Controller is developed by integrating the VSS and FLC. On analyzing these various controller actions on the power plants, it is found that Variable Structure Fuzzy Logic Controller yields better transient and steady state response than any other controller for all the power plants.